In my opinion some things may be. For instance physical things. The monks in the shaolin temple have been implementing a sort of "mind over matter" for years. Now dont get me wrong, the physically impossible cannot be achieved, It is more a case of how far can we stretch possible. For instance you nor I could break a concrete block with out head, yet they could and I personally believe that alongside years of conditioning a mental attitude of If I imagine it, it is possible go hand in hand. I also know of no math that can explain these feats which would 99% of the time be deemed impossible. Look up the 72 shaolin secret martial arts. As for "I can imagine flying, So I can do it." I dont believe in it because it simply does not work.